1. Field of the Invention
The present invention relates to an elongated cutting tool used in wood working devices such as veneer lathes and veneer slicers, and also to an apparatus for and a method of grinding such an elongated cutting tool.
2. Description of the Related Art
An elongated cutting tool 2 conventionally used for wood working has a sloping surface `a` and a non-sloping surface `b` as shown in FIG. 17, and a cutting edge thereof 2 has an acute angle as 20 through 30 degrees.
Such a conventional cutting tool generally has a thin and sharp cutting edge. When the thin cutting edge of the cutting tool hits against a knot or another hard portion of a log in the cutting process, an excessive load is applied onto the cutting edge. The cutting edge is thereby pressed back outwardly to separate from the log and then inwardly onto the log surface as a counteraction. The sharper cutting edge causes greater vibration of the cutting edge due to the press-back and press-on cycle. Such vibration results in the uneven thickness of a veneer cut from the log and undesirably damages the cutting edge hit against a knot, a resin pocket, or another hard portion of the log.
The applicant of the present invention has proposed an improved method of superfinishing a cutting edge, wherein the cutting edge of an elongated cutting tool is finished to have a curved surface by multiple-taper grinding as disclosed in JAPANESE PATENT LAYING-OPEN GAZETTE No. 63-99163. This method attains a thicker cutting edge with sufficient cutting quality.
The elongated cutting tool having a cutting edge superfinished according to the above method has greater angle and thickness than the conventional cutting tool to give longer service life. Improvement in the angle and thickness of the cutting edge is, however, not sufficient, which still causes unstable cutting or vibration of the cutting edge against the cut surface of the log.
In order to prevent vibration of the sharp cutting edge, a tip of a non-sloping surface of the cutting tool is ground off by a certain angle. Although this grinding procedure reduces the vibration of the cutting edge to some extent, the ground tip of the non-sloping surface slides against a rear side of a veneer currently cut from the log to damage or even crack the rear side of the veneer.